The primary transcript of one of the two chorismate synthase genes (LeCS2) of tomato is differentially processed due to an alternative splicing of the third intron. A novel observation was made when the abundances of the two LeCS2-specific transcripts in different organs were analysed. The ratio of these two transcripts differs in RNA populations from different organs. Possible explanations for this finding and its potential physiological impact for plant metabolism are discussed.

In tomato (Lycopersicon esculentum L. cv. UC82b) two distinct genes (designated LeCS1 and LeCS2) code for chorismate synthase. The corresponding cDNAs have been isolated and characterized. The deduced amino acid sequences are 88% identical. Both genes encode chorismate synthases with putative plastid-specific N-terminal transit peptides. The two genes are predominantly expressed in flowers and roots and, to a lesser extent, in stems, leaves, and cotyledons, but the steady-state levels of LeCS1-specific transcripts are consistently higher than those of the LeCS2-specific transcripts.